1. Field of the Invention
The present invention relates to a processor having turbo modes that allow the processor to automatically increase or decrease its clock speed.
2. Background of the Related Art
A processor is a synchronous circuit that operates at a frequency measured in hertz (cycles per second) and know as the clock rate. After manufacturing, each processor is tested to determine the clock rate at which the processor can pass certain standards of performance. Accordingly, the processor is labeled and sold as operating at a given clock rate. A user, however, may alter the clock rate to achieve one or more objective. The clock rate may be slowed (i.e., “underclocking”) to reduce the amount of waste heat generated by the processor or increased (i.e., “overclocking”) to increase performance of the processor.
Certain processors made by Intel Corporation, for example the Core i5 and Core i7 processors, allow the processor's performance to be dynamically increased on demand. According to Intel, when the processor is operating below its thermal and electrical limits and the user's workload demands additional performance, the processor clock frequency will dynamically increase incrementally until the upper limit of the processor's clock frequency is met or until the maximum possible upside for the number of active cores is reached. Conversely, when any of the limits are reached or exceeded, the processor clock frequency will automatically decrease incrementally until the processor is again operating within its limits.
Processors that are capable of running at clock rates or frequencies greater than the base operating frequency, such as the Intel Core i5 and i7 processors discussed above, may be placed in a turbo boost state at the request of the operating system. For example, where the operating system is aware of ACPI (Advanced Configuration and Power Interface) states, the operating system may cause the processor to operate at a specific performance state. Optionally, the maximum processor power and frequency state (P0) may be used to put the processor into a turbo boost state where the processor may operate across a plurality of frequency steps (or turbo modes) above the base operating frequency. The base operating frequency is the mathematical product of an external clock rate and a clock multiplier, such that in one example an external clock rate of 133 MHz and a clock multiplier of 10 will operate the processor at 1.33 GHz. However, when the processor in a turbo boost state, the processor may operate above the base operating frequency in steps, such as frequency steps equal to the external clock rate of 133 MHz. Accordingly, when the processor is in the turbo boost state, the actual internal clock rate or operating frequency of the processor may be described by indicating the integer number of steps (i.e., bin upside) above the base operating frequency. A bin upside of “bin +1” means that the processor is operating at one frequency step above the base operating frequency (for example, 1.33 GHz+1*133 MHz=1.463 GHz), and a bin upside of “bin +2” means that the processor is operating at two frequency steps above the base operating frequency (for example, 1.33 GHz+2*133 MHz=1.596 GHz).
In a multi-core processor, the number of active cores at any given instant will dictate the upper limit of turbo modes. For example, a four-core processor having only one active core at a given instant may be able to operate at a higher turbo mode than when all four cores are active. For example, a core may be considered to be active if it is in the ACPI C0 or C1 power states, whereas a core may be considered to be inactive if it is in the ACPI C3 or C6 states. Therefore, a four-core processor may be rated for a turbo mode of 1/1/6/9 where the upper turbo mode for 4 active cores is bin +1, the upper turbo mode for 3 active cores is also bin +1, the upper turbo mode for 2 active cores is bin +6, and the upper turbo mode for 1 active core is bin +9. Other processors may have other ratings.